Setaria incrassata


Scientific name

Setaria incrassata (Hochst.) Hack.

Synonyms

Setaria gerrardii Stapf
Setaria holstii R. A. W. Herrm.
Setaria perberbis Stapf ex de Wit
Setaria phanerococca Stapf
Setaria woodii Hack.

Many other synonyms are proposed in Flora of Tropical East Africa and Grasses of Southern Africa, including Setaria porphyrantha Stapf (see cv. Inverell).

Family/tribe

Family: Poaceae (alt. Gramineae) subfamily: Panicoideae tribe: Paniceae.

Common names

purple pigeon grass (Australia);  vlei bristle grass (South Africa);  canary millet (Zimbabwe).

Morphological description

A shortly rhizomatous (praemorse rhizome), tufted perennial, with geniculately ascending culms 30-200 cm high;  nodes usually hairy.  Leaf blades flat or convolute, linear, 10-60 cm long and 3-15 mm wide, tapering to a long fine point.  Inflorescence a dense, continuous false spike 3-30 cm long, 8 mm wide (excluding the bristles);  bristles 2-15 mm long;  spikelets broadly ovate , 2.5-3 (-3.7) mm long.  560,000 seeds/kg.

Distribution

Native to:
Africa:  Angola, Botswana, Cameroon, Ethiopia, Lesotho, Malawi, Mozambique, Namibia, Nigeria, South Africa, Swaziland, Tanzania, Uganda, Zambia, Zimbabwe.
Occurs in a wide range of habitats, primarily on black clays plains, but also on stony hillsides, in grassland, along stream banks, and in swamp and forest margins.

Uses/applications

Sown as a medium to long-term pasture , and for erosion control on black earths where other perennials are of limited value because of establishment difficulties.  Speed and reliability of establishment make it ideal for short-term leys.

Ecology

Soil requirements

Mostly found on black clay soils, but has also been collected on clay loams, sandy loams and sands.  These soils are mostly well drained, but sometimes with impeded drainage.  PH at collection sites varies from 6.2-8.2.  The main limitation appears to be the need for high soil fertility .  In cultivation, established stands decline as fertility falls.

Moisture

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Occurs naturally in moister situations in areas receiving annual rainfall from about 500 to >1,200 mm.  Similar drought tolerance to that of Panicum coloratum var makarikariense, but less than that of Cenchrus ciliaris .  It establishes more readily without irrigation than most other introduced warm season perennial grasses, even under conditions of fairly severe moisture stress.  It can tolerate short periods of waterlogging , but is inferior to P. coloratum var makarikariense in this respect.

Temperature

Occurs from 34ºS-5ºN, and from near sea level to 2,400 m aslAnnual average temperature in the coolest part of this range is about 16ºC, often with heavy frosts.  It has been successfully cultivated from about 24-33ºS in Australia, producing well in mid-summer.  Spring, autumn, and total growth is slightly inferior to that of P. coloratum var makarikariense.  'Inverell' is very susceptible to frost damage but mostly recovers with the onset of warmer conditions.

Light

Grows best in full sunlight.

Reproductive development

Flowers throughout the growing season given adequate moisture.

Defoliation

It does not survive continuous heavy grazing.

Fire

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Recovers following fire, from both tussocks and seed.

Agronomy

Establishment

Freshly harvested seed can remain dormant for 7-18 months and should be tested before sowing.  Summer sowings are usually more successful, although more dormant seed can be sown with winter cereals allowing it to establish the following spring.  In general it should be sown at 2-3 kg seed/ha into a well-prepared seedbed, to a depth of 1-2 cm or slightly deeper (3-4 cm) in self-mulching soils.  If there is moisture at depth, seedlings can emerge from as deep as 5 cm, but planting at this depth is generally not recommended.  Subsequent rolling is usually beneficial, but not on crusting soils or if increased erosion risk is evident.  On heavy clay soils or seed production plots, a sowing rate of 4 kg/ha of seed can be used to hasten results.  It is a large, free-flowing seed which can be sown through crop or pasture planters.  'Inverell' establishes readily on black clay soils, even under moisture stress conditions where other species fail completely.

Fertiliser

Application of 100-200 kg/ha of superphosphate at planting can be beneficial in soils of low to moderate phosphorus fertility.  There is usually adequate nitrogen released during cultivation to satisfy initial demands, but nitrogenous fertiliser may be essential subsequently if legume nitrogen is insufficient to maintain stand.

Compatibility (with other species)

Grows well with legumes and other grasses, but can initially suppress more slowly establishing companions if seeding rate of S. incrassata is too high.

Companion species

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Grasses:  Chloris gayana , Panicum coloratum , Panicum maximum .
Legumes:  Clitoria ternatea , Desmanthus leptophyllus , D. virgatus , Medicago sativa , M. truncatula, M. scutellata, Trifolium subterraneum,
Other:  Cichorium intybus.

Pests and diseases

No problems encountered.

Ability to spread

Seedling recruitment is common within a stand.

Weed potential

Spread beyond planted areas has so far given little cause for concern.

Feeding value

Nutritive value

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P levels ranging from 0.12-0.41%, and Ca levels from 0.14-0.29%.

Palatability/acceptability

Not as palatable as other grasses sown on black clay soils, although has satisfactory palatability when young.  It is readily eaten when fed as hay .

Toxicity

Total oxalate levels vary from 0.67-1.9% of the dry matter, with Ca : total oxalate ratio from 0.09-0.24 (Note Ca : total oxalate levels <0.5 are considered to be potentially capable of causing bighead disease in horses unless Ca supplements are provided).

Production potential

Dry matter

Productivity in the first and second year of establishment is superior to that of most other perennial grasses in the same environment.

Animal production

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Comparable liveweight gains to those achieved from other grasses.  Mostly used for cattle production, but is also grazed by sheep.

Genetics/breeding

  

Seed production

Stubble is gradually reduced by grazing, before cutting remaining material to about 10 cm.  The crop can be started at any time during the growing season when soil moisture is likely to be adequate for the 60-90 days it takes for the crop to develop, and before the likelihood of frost damage to the developing crop.  Best crops are achieved using irrigation and an initial application of 100 kg/ha N, although lower rates of N (30-50 kg/ha) can be used if moisture is likely to be limiting.  Seed is ready to harvest when it feels gritty and the colour changes from purplish green to light green.  Seed reaches a peak of ripeness over a period of 4-10 days, after which it readily falls.  Timing of harvest is therefore crucial.  With good summer rainfall , yields in the order of 200-300 kg/ha/year can be expected from two harvests in a season, and up to 390 kg/ha have been obtained.  Presentation yields of about 600 kg/ha/crop have been measured, with potential (total) yields of over double this figure.  Direct heading is most common although swathing and pick-up with a draper front header has been used to great effect by specialist seed producers.

Herbicide effects

No information available.

Strengths

  • Easy to establish on heavy black soils.
  • Drought tolerant.
  • Tolerant of temporary waterlogging .

Limitations

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  • Needs moderate to high fertility.
  • Doubtful palatability .
  • Oxalate levels that could harm horses.
  • Intolerant of heavy grazing.

Other comments

  

Selected references

Clayton, W.D. and Renvoize, S.A. (1982) Gramineae (Part 3). In: Polhill, R.M. (ed.) Flora of tropical East Africa. pp. 525-527. (A.A. Balkema on behalf of the East African Governments, Rotterdam, Netherlands).
Gibbs Russell, G.E., Watson, L., Koekemoer, M., Smook, L., Barker, N.P., Anderson, H.M. and Dallwitz, M.J. (1990) Grasses of Southern Africa. Memoirs of the Botanical Survey of South Africa No. 58. p. 296. (Botanical Research Institute: Pretoria.).
McKenzie, R.A. (1988) Purple pigeon grass (Setaria incrassata ): a potential cause of nutritional secondary hyperparathyroidism of grazing horses. Australian Veterinary Journal, 65, 329-330.
Watt, L.A. (1976) Evaluation of pasture species for soil conservation on cracking black clays, Gwydir district, N.S.W. Journal of Soil Conservation , N.S.W, 32, 86-97.

Internet links

Cultivars

Cultivars

Country/date released

Details

'Inverell'
(CPI 24582)
Australia (1977) Institutional collection from Matopos Research Centre, Zimbabwe.  Leafy variety 0.6-1.5 m high, leaves glaucous.  Released as a forage for permanent and ley systems in sub-humid, subtropical eastern Australia.

Promising accessions

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Promising accessions

Country

Details

None reported.